Setting up a boat trailer

[Avocet]

no NO NO ! Please do not use the tyre pressures to adjust the nose weight.

Air in the tyres is meant to support a given mass (the tyres will have the maximum load and pressure engraved in the side) If you reduce the tyre pressure, the side walls will flex excessively, overheat, and blow out.

To check what I am saying, lower the pressure in one of your car tyres to half the normal. Drive a mile, slowly, then check the wall temperature. Then pump it back up.

You must get the balance of the load in relation to the axles right.


FWIW, even using my 30ft three axle trailer, I load the boat so that the nose weight is about 50kg (enough for it to be starting to be difficult to lift)

If that was the case, car tyres would be blowing out all over the place when people didn't up the pressures as they carried more load! What you say is true, in theory, and in an earlier post, I did advise not overdoing it for precisely the reason you cite, but in practice, a few PSI difference (say 10% in a tyre that's supposed to run at 50 PSI) isn't going to be a problem.

 

[lw395]

I'd be interested to hear how you get on. Obviously, driver licensing is one thing, (and I could see the sense in that relating to a theoretical maximum), but when it comes to the "in-use" situation, I think it's utterly barmy!

In the extreme case, I can see a little sense in it.
An empty heavy trailer will have stiff suspension and tyres at high pressure.
They can get very bouncy which could get scary with a small car.
Even an empty dinghy trailer can get a bit out of shape on bumpy corners and upset the car.
I wouldn't want to push it in the wet.

A lot of these issues are down to trailer suspension being a bit of a sick joke. The nose weight would not be so sensitive to the hitch height if the suspension was not basically far too hard. But soft springs would mean you'd need proper dampers.

Take care.

 

[Avocet]

I think this might be wrong.
The principle behind having nose weight, as I understand it, is that the centre of mass of the trailer should be a bit forward of the vector where the tyres are providing lateral resistance.
By having wrong tyre pressures, you may force the nose weight to be right, but the lateral force from the tyres could be unpredictable.
Nose weight is mainly an indicator that the centre of mass is in the right place, not a goal in itself.

Personally, I find towing very heavy trailers a bit of a worry and would be reluctant not to have it fairly spot on.

The C of G certainly should be ahead of the centre of lateral resistance, but unless the OP wants to move either his boat or his axles, that's not something we can do anything about. A bit of nose weight is good for keeping a downward load on the rear axle of the towing vehicle (which can also help improve stability of the outfit as a whole), but we're talking about different things. So far, all we have to go on is that there appeared to be no nose weight when the boat is on the trailer. We still don't know that this will actually create any problems when towing, we just suspect it might. You certainly wouldn't want the C of G to be MUCH ahead of midway beween the axles!

Come to think of it, I'm not even sure where the "Centre of Lateral Resistance" of a trailer when hitched up to a towing vehicle would be!

 

[Avocet]

In the extreme case, I can see a little sense in it.
An empty heavy trailer will have stiff suspension and tyres at high pressure.
They can get very bouncy which could get scary with a small car.
Even an empty dinghy trailer can get a bit out of shape on bumpy corners and upset the car.
I wouldn't want to push it in the wet.

A lot of these issues are down to trailer suspension being a bit of a sick joke. The nose weight would not be so sensitive to the hitch height if the suspension was not basically far too hard. But soft springs would mean you'd need proper dampers.

Take care.

Yes, but away from boat trailers (which generally either run at zero or maximum capacity), most other sorts of trailer run at vastly varying weights. My dropside is very old (old enough to have simple, non-auto-reverse spring over-run brakes) and can probably weigh up to about 3 tonnes laden without doing itself any damage. I never use it with that kind of weight. My car can only tow up to 2 tonnes. I have no wish to endanger myself (or anyone else!) and wouldn't want to tow more than that. However, if such a law DID exist, I'd just have to make up a plate that had a maximum weight on it that was equal to the max. towing weight of whatever car I happened to be towing it with!

 

[maxi77]

I've heard this a few times too, but nobody has ever been able to point me at the bit of legislation that says it! To be honest, I'm beginning to think it's one of those motoring myths. Let's face it, just looking at it from a "common sense" point of view, it would be utterly bizarre! It would be like making it illegal to posess a car that was capable of exceeding the speed limit - even though you weren't driving it in excess of the speed limit at the time! What next? Making it illegal to own a car if it isn't capable of carrying all the members in your family and their combned luggage?

Even so most towing sites do advise against it. As far as I have been able to find out it is untested in law but it does give old Mr Plod an excuse to cause you hassle. Illogical it may be but ubtil it is properly tested it is an are of risk.

 

[maxi77]

The C of G certainly should be ahead of the centre of lateral resistance, but unless the OP wants to move either his boat or his axles, that's not something we can do anything about. A bit of nose weight is good for keeping a downward load on the rear axle of the towing vehicle (which can also help improve stability of the outfit as a whole), but we're talking about different things. So far, all we have to go on is that there appeared to be no nose weight when the boat is on the trailer. We still don't know that this will actually create any problems when towing, we just suspect it might. You certainly wouldn't want the C of G to be MUCH ahead of midway beween the axles!

Come to think of it, I'm not even sure where the "Centre of Lateral Resistance" of a trailer when hitched up to a towing vehicle would be!

I can asure you that low nose weight will seriously affect handling, you can try it if you like but I would advise not exceeding about 15mph. You see when the static loads become dynamic they can really create serious problems

 

[sarabande]

If that was the case, car tyres would be blowing out all over the place when people didn't up the pressures as they carried more load! What you say is true, in theory, and in an earlier post, I did advise not overdoing it for precisely the reason you cite, but in practice, a few PSI difference (say 10% in a tyre that's supposed to run at 50 PSI) isn't going to be a problem.

For the purposes of the empirical demonstration that reduced pressure means overheating, I did not mention 10% or "few".

 

[Avocet]

Maxi 77, I've been there, done that. Sometimes it's Ok sometimes it isn't. Whilst I broadly agree that "some" nose weight is good, and that negative nose weight is always bad (for a variety of reasons), and that in GENERAL, increasing nose weight improves stability, I have not always found it to be the case. My personal experience of it is that nose weight is only one of the factors that determines the stability of the trailer and vehicle.

 

[Avocet]

For the purposes of the empirical demonstration that reduced pressure means overheating, I did not mention 10% or "few".

If you mean vastly reduced pressure, then (as I've already said) I agree with you entirely. That's not what was being discussed though.

 

[Lakesailor]

I've heard this a few times too, but nobody has ever been able to point me at the bit of legislation that says it! To be honest, I'm beginning to think it's one of those motoring myths. Let's face it, just looking at it from a "common sense" point of view, it would be utterly bizarre! It would be like making it illegal to posess a car that was capable of exceeding the speed limit - even though you weren't driving it in excess of the speed limit at the time! What next? Making it illegal to own a car if it isn't capable of carrying all the members in your family and their combined luggage?

I once tried to hire a trailer from Indespension at their HQ in Bolton. They refused on the basis that my car did not have a Towing Weight greater than the Gross Trailer Weight of the car trailer I wanted to hire.
I pointed out that I was carrying mini which weighed less than 700Kgs and that the outfit would come under my vehicle's Towing Weight.
They insisted that it was the weight stamped on the trailer plate which was the decider, not the loaded weight.
Their designer came down to argue the point. We had some Anglo Saxon based discussions about it.

I later found out that they were correct. Alistairr of these forums found out the same when buying a trailer for his business. You are quite entitled to have a new plate made with a GTW within your vehicle's towing limit. Of course you can only load the trailer up to that weight then.

The point is that few plod know any of this and even their civilian vehicle examiners are a bit sketchy on the law.

 

[ProDave]

Interesting points.

I once hired a twin axle car trailer, and the hire co were a little uneasy as the MAM of the trailer was greater than the towing capacity of my car. But when I explained it was only going to be carrying a mini, they were happy to hire it to me.

I always thought it was the ACTUAL weight of the trailer that mattered. If Mr Plod stops you and there is any doubt, it will be off to a weighbridge, and the actual weight of the trailer will determine if an offence has been comitted or not.

 

[lw395]

Interesting points.

I once hired a twin axle car trailer, and the hire co were a little uneasy as the MAM of the trailer was greater than the towing capacity of my car. But when I explained it was only going to be carrying a mini, they were happy to hire it to me.

I always thought it was the ACTUAL weight of the trailer that mattered. If Mr Plod stops you and there is any doubt, it will be off to a weighbridge, and the actual weight of the trailer will determine if an offence has been comitted or not.

If the actual weight exceeds the allowed weight that's one offence, if the plated max mass exceeds that allowed for the towing vehicle, that's a different offence, which doesn't involve the plod with the hassle of going to a weighbridge. The paper trail is so much easier to police than the real world!

In practice, it probably doesn't matter unless you are taking it to extremes, like towing an empty 3500kg yacht trailer with a small car. But its the kind of thing that could turn a minor speeding caution into a big deal.

 

[Avocet]

Fair enough, I can see the point about the paper trail being easier. I'd also be reluctant to get into an argument with Indespension's chief designer, but I'd still like to know what regulation stipulates this! (And in the course of my day job, I tend to be deeply suspicious of people who tell me something's illegal but then can't point to where it says so)! I'm fairly certain I know where to find the regulation that says an offence has been committed if what's being towed at the time you're stopped is in excess of the Gross Train Weight on the vehicle's chassis plate, but this other offence, if it exists, isn't in the same section. There was a bit of talk in Brussels about having a max permitted trailer weight as a separate item on the chassis plate, to stop people from towing a trailer that's really too heavy, with an empty car to keep the whole lot within Gross Train Weight, but I'm not sure anything ever came of it.

Still, the great thing about having an old trailer, and no compulsory registration scheme for trailers, is that if they want to play silly bu99ers just to make the paperwork easier, I can do it too!

 

[GrahamHR]

This all seems a really silly interpretation, with no basis in common sense whatsoever; assuming my car is allowed to tow say 2,000kg, I can tow a trailer loaded up to 2,000kg total trailer + load, but not a 600 kg trailer designed to carry an additional 1,401 kg ?

 

[maxi77]

Maxi 77, I've been there, done that. Sometimes it's Ok sometimes it isn't. Whilst I broadly agree that "some" nose weight is good, and that negative nose weight is always bad (for a variety of reasons), and that in GENERAL, increasing nose weight improves stability, I have not always found it to be the case. My personal experience of it is that nose weight is only one of the factors that determines the stability of the trailer and vehicle.

Oh indeed, dodgy brakes can really spoil your day and so on. With a caravan I found there tended to be a relatively narrow band of noseweight from the minimum you could get away with to the max the tow vehicle was supposed to take, Mind you with a caravan you did want to be able to go at 60 on the motorways. It also depends on the tow vehiclesome are a lot less sensitive than others, my mates Disco is very tolerant whereas the Multipla was very senstive.

Why the guy insists on carrying 250 kgs of fuel at the stern knowing he has a nose weight proble still amazes me especially as that lot sloshing at the other end of the rig can't improve stability

 

[Lakesailor]

Fair enough, I can see the point about the paper trail being easier. I'd also be reluctant to get into an argument with Indespension's chief designer, but I'd still like to know what regulation stipulates this! (And in the course of my day job, I tend to be deeply suspicious of people who tell me something's illegal but then can't point to where it says so)! I'm fairly certain I know where to find the regulation that says an offence has been committed if what's being towed at the time you're stopped is in excess of the Gross Train Weight on the vehicle's chassis plate, but this other offence, if it exists, isn't in the same section. There was a bit of talk in Brussels about having a max permitted trailer weight as a separate item on the chassis plate, to stop people from towing a trailer that's really too heavy, with an empty car to keep the whole lot within Gross Train Weight, but I'm not sure anything ever came of it.

Still, the great thing about having an old trailer, and no compulsory registration scheme for trailers, is that if they want to play silly bu99ers just to make the paperwork easier, I can do it too!

I was similarly suspicious. It may have been back-covering by Indespension. However, the points of law have been pointed out to me since. That said I can't find the regulations proving it now.
I guess the reasonable thing is to make sure you look right. That's the reason plod will pull you. If it looks wrong.

 

[VicS]

I have a close coupled 4 wheel trailer.

I have never known what to do about nose weight

I still dont

Fortunately I dont often use it. 3 times 30 miles and 2 times 80 mils in 35 years.

If I use it once more that will be the last time I'd guess.

It tows like drunken boa constrictor !

 

[ProDave]

I have a close coupled 4 wheel trailer.

I have never known what to do about nose weight

I still dont

Fortunately I dont often use it. 3 times 30 miles and 2 times 80 mils in 35 years.

If I use it once more that will be the last time I'd guess.

It tows like drunken boa constrictor !

Nose weight or tow ball height. Read and understand this thread.

 

[Jim@sea]

You may find that the trailer is undersized for your boat. Boatyards dont always know everything and the new trailer which I was advised to buy when I bought a new boat from a Boatyard in St Malo was inappropriate for the Boat they sold me.
And it was set up wrongly. I assumed that the combination was road legal but it was not. So in fact the Trailer and Boat carried on it would not have been insured (in the event of a claim)
The trailer was nose heavy. I was able to move the axles back about 9" which balanced the boat perfectly. But in doing so I thought the tyres seemed to bulge more than they should. So I went to a weighbridge and found that after taking the 1000 kilos off the combined weight that the boat weighed 400 kilos more than the trailer was designed to carry.
The boatyard had totally underestimated the weight of the boat they were selling me.
In your case I would suggest you ring the trailer manufacturer and give them the make of your boat and ask what size trailer they recommend and see if is the model you have
PS. As I do a lot of towing once I have a heavy boat on a trailer I always go to a weighbridge and weigh it just once, just in case I am stopped.

 

[Lakesailor]

PS. As I do a lot of towing once I have a heavy boat on a trailer I always go to a weighbridge and weigh it just once, just in case I am stopped.

A good idea.
I've only done it once, but with small boats I can do it at home, for free.
Present boat weighs 470kgs on trailer, with motor.